A 6 month intervention study involving 370 post menopausal women who have been treated for breast cancer is proposed. Randomized women, stratified by resected stage, systemic adjuvant therapy and body mass index (> 25 and < 35 Kg/m2), will serve as either a non-intervention control group or will follow a tailored diet-physical activity program designed to create a weekly negative energy balance equivalent to 3500 kcal. The intervention groups will receive the same physical activity protocol, but one of two diets that differ in dietary pattern.